Method for controlling dehydration speed of washing machine

ABSTRACT

The present invention discloses a method for controlling a dehydration speed of a washing machine which can reduce vibrations and noises of the washing machine. The method for controlling the dehydration speed of the washing machine includes the steps of: setting the dehydration speed on the basis of an amount of laundry put into the washing machine; and controlling a rotation speed of a motor of the washing machine on the basis of the set dehydration speed.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a washing machine, and moreparticularly, to a method for controlling a dehydration speed of awashing machine.

[0003] 2. Description of the Background Art

[0004] In general, when detergent, water and laundry are put into awashing machine, especially a drum washing type washing machine, thewashing machine washes the laundry by using a frictional force between adrum rotated by a driving force of a built-in motor and the laundry. Inthe drum washing type washing machine, the laundry is rarely damaged andtangled, and washing effects are improved as if the laundry was beatenand rubbed.

[0005] The structure of the conventional drum washing machine will nowbe explained with reference to FIG. 1.

[0006]FIG. 1 is a cross-sectional diagram illustrating the conventionaldrum washing machine.

[0007] Referring to FIG. 1, the drum washing machine includes a tub 3installed inside a cabinet 5, a drum 9 installed inside the tub 3, adrum shaft 13 directly coupled to the drum 9, for transmitting a drivingforce of a motor 6 to the drum 9, bearings 12 installed in the front andrear sides of the drum shaft 13, a bearing housing (not shown) installedin the center of the rear wall of the tub 3, for supporting the bearings12, a stator 7 installed on the rear wall of the tub 3, for forming themotor 6, a rotor 8 installed on the drum shaft 13, for forming the motor6 with the stator 7, a door 1 installed in the front side of the cabinet5, a gasket 2 installed between the door 1 and the tub 3, a hangingspring 4 installed between the inside of the top surface of the cabinet5 and the upper side of the outer circumference of the tub 3, forsupporting the tub 3, a friction damper 10 installed between the insideof the bottom surface of the cabinet 5 and the lower side of the outercircumference of the tub 3, for damping vibrations of the tub 3 duringthe dehydration, and a motor sensor 11 installed in one side of themotor 6, for sensing a rotation speed of the rotor 8. Here, the rotationspeed of the rotor 8 implies the rotation speed of the motor 6.

[0008] A conventional method for controlling a dehydration speed of adrum washing machine will now be described.

[0009] When a mode of the washing machine is changed into a dehydrationmode and the rotor 8 is rotated, the motor sensor 11 continuously sensesthe rotation speed of the rotor 8, and outputs the sensed speed to acontroller (not shown).

[0010] The controller compares the rotation speed of the rotor 8 sensedby the motor sensor 11 with a preset rotation speed, and controls therotation speed of the rotor 8 according to a dehydration speed suitablefor the dehydration mode selected by the user.

[0011] The dehydration mode will now be explained in more detail.

[0012] The laundry is washed in a washing rotation speed (for example,about 45 rpm to 50 rpm(rpm: Revolution Per Minute)). To dehydrate thewashed laundry, the rotation speed of the drum 9 connected to the rotor8 is increased to about 100 rpm by increasing the rotation speed of therotor 8. The laundry is dehydrated in the rotation speed. That is, thecontroller (not shown) dehydrates the laundry by increasing the rotationspeed of the rotor 8 to the dehydration speed set by the user (800 rpmor 1400 rpm).

[0013] However, the conventional washing machine includes a brushlessdirect current (BLDC) motor for converting the dehydration speedaccording to a kind of cloth or upon the user's request, which increasesvibrations and noises. For example, if the rotation speed of the motoris controlled in the preset dehydration speed, regardless of a kind andamount of laundry put into the washing machine, even when the laundry issmall, the motor is operated in the preset dehydration speed, therebyincreasing vibrations and noises of the washing machine.

[0014] In addition, the conventional washing machine has the BLDC motorfor converting the dehydration speed according to a kind of cloth orupon the user's request, which increases manufacturing expenses.

SUMMARY OF THE INVENTION

[0015] Therefore, an object of the present invention is to provide amethod for controlling a dehydration speed of a washing machine whichcan reduce vibrations and noises of the washing machine.

[0016] Another object of the present invention is to provide a methodfor controlling a dehydration speed of a washing machine which canreduce vibrations and noises of the washing machine, by setting thedehydration speed on the basis of an amount of laundry put into thewashing machine, and controlling a rotation speed of a motor accordingto the set dehydration speed.

[0017] Yet another object of the present invention is to provide amethod for controlling a dehydration speed of a washing machine whichcan reduce vibrations and noises of the washing machine, by changing anumber of poles of a motor of the washing machine, and controlling avoltage applied to the motor when the number of the poles is changed.

[0018] Yet another object of the present invention is to provide amethod for controlling a dehydration speed of a drum washing machinewhich can reduce vibrations and noises of the drum washing machine andcut down manufacturing expenses of the drum washing machine, by changinga number of poles of an induction motor of the drum washing machine, andcontrolling a voltage applied to the induction motor when the number ofthe poles is changed.

[0019] To achieve these and other advantages and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, there is provided a method for controlling a dehydration speedof a drum washing machine, including the steps of: setting thedehydration speed on the basis of an amount of laundry put into thewashing machine; and controlling a rotation speed of a motor of thewashing machine on the basis of the set dehydration speed.

[0020] The foregoing and other objects, features, aspects and advantagesof the present invention will become more apparent from the followingdetailed description of the present invention when taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0022] In the drawings:

[0023]FIG. 1 is a vertical-sectional diagram illustrating a conventionaldrum washing machine;

[0024]FIG. 2 is a flowchart showing a method for controlling adehydration speed of a drum washing machine in accordance with thepresent invention;

[0025]FIG. 3 is an exemplary diagram illustrating conversion of a numberof poles of a stator of a motor of the drum washing machine inaccordance with the present invention; and

[0026]FIG. 4 is a graph showing torque-speed curves of the motor in themethod for controlling the dehydration speed of the drum washing machinein accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0028] A method for controlling a dehydration speed of a washing machinewhich can reduce vibrations and noises of the washing machine bychanging a number of poles of a motor of the washing machine, andcontrolling a voltage applied to the motor when the number of the polesis changed will now be described in detail with reference to FIGS. 2 to4.

[0029]FIG. 2 is a flowchart showing the method for controlling thedehydration speed of the drum washing machine in accordance with thepresent invention.

[0030] As illustrated in FIG. 2, the method for controlling thedehydration speed of the drum washing machine includes the steps of:inputting a preset dehydration speed by the user (S11); confirming therange of the input dehydration speed (S12); changing a number of polesof an induction motor installed in the drum washing machine according tothe range of the dehydration speed (S13 and S17); converting thedehydration speed by controlling a phase of a voltage inputted to theinduction motor installed in the drum washing machine, when the numberof the poles of the motor is changed (S14 and S18); calculating thedehydration speed converted by changing the number of the poles of themotor and controlling the phase, and a torque and efficiency of theinduction motor (S15 and S19); and evaluating performance satisfactionof the induction motor on the basis of the torque and efficiency of theinduction motor (S16 and S20).

[0031] The operation of the method for controlling the dehydration speedof the drum washing machine in accordance with the present inventionwill now be described in more detail.

[0032] The user inputs the preset dehydration speed according to adehydration course (S11). Here, when the user puts the laundry into thedrum washing machine, a hall sensor (not shown) installed inside thedrum washing machine senses a kind and amount of the laundry on thebasis of the rotation speed of the motor, and sets the dehydration speedaccording to the kind and amount of the laundry (S12). The amount of thelaundry can be sensed on the basis of the rotation speed of the motormeasured when the motor is rotated in the preset rotation speed.

[0033] Thereafter, the range of the dehydration speed inputted by theuser is confirmed. When the input dehydration speed is 800 rpm, thenumber of the poles of the motor is changed into 8, and then the motoris operated. That is, when the motor has 8 poles, the rotation speed ofthe motor is 800 rpm. Here, the rotation speed of the motor can becontrolled between 400 rpm and 800 rpm by controlling the voltageapplied to the motor by controlling the phase of the voltage when themotor is changed to have 8 poles.

[0034] Conversely, when the input dehydration speed is 1400 rpm, thenumber of the poles of the motor is changed into 4, and then the motoris operated. That is, when the motor has 4 poles, the rotation speed ofthe motor is 1400 rpm. Here, the rotation speed of the motor can becontrolled between 1000 rpm and 1400 rpm by controlling the voltageapplied to the motor by controlling the phase of the voltage when thestator of the motor is changed to have 4 poles.

[0035] Therefore, the dehydration speed can be variously converted bychanging the number of the poles of the stator of the motor, andconverting the voltage applied to the motor when the number of the polesis changed. In the related arts, the rotation speed of the motor iscontrolled according to the preset dehydration speed, regardless of thekind and amount of the laundry put into the washing machine.Accordingly, even when the laundry is small, the motor is operated inthe preset dehydration speed, to increase vibrations and noises of thewashing machine. However, in accordance with the present invention, thedehydration speed is set on the basis of the amount of the laundry putinto the washing machine, and the rotation speed of the motor iscontrolled according to the dehydration speed, which reduces vibrationsand noises of the washing machine.

[0036] The phase control will now be explained in detail with referenceto FIG. 4. FIG. 4 is a graph showing torque-speed curves of the motor inaccordance with the present invention. As shown in FIG. 4, the laundryis dehydrated by rotating the drum in the dehydration speed N₁, N₂ andN₃ where a load torque T_(L) meets input voltage V₁, V₂ and V₃ appliedto the motor, by adjusting the input voltage V₁, V₂ and V₃ bycontrolling the phase. Here, the load torque T_(L) is a torque appliedto the drum.

[0037] The phase control of the present invention will now be describedin more detail.

[0038] A Triac device which is a gate control semiconductor switch foralternating current power included in a phase control circuit is used tovary the speed of the induction motor when sine input voltage waveform,namely single phase power (for example, 220V/60 Hz) is applied. That is,the operation speed of the motor is converted by adjusting the outputvoltage V₁, V₂ and V₃ by controlling a fire angle according to the inputpulse signal of the Triac device.

[0039] In the case of the method for controlling the dehydration speed,when the dehydration speed selected by the user is 400 rpm, the numberof the poles of windings of the stator is changed into 8, and the inputvoltage V₃ is applied to the motor as shown in the torque-speed curvesof FIG. 4, and when the dehydration speed selected by the user is 600rpm, the number of the poles of the motor is changed into 8, and theinput voltage V₂ is applied to the motor. In addition, when thedehydration speed selected by the user is 800 rpm, the number of thepoles of the windings of the stator is changed into 8, and the inputvoltage V₁ is applied to the motor. That is, the dehydration speed 800rpm approximately obtained in the 8 poles of the stator can be varied inmultiple steps by changing the input voltage applied to the motor bycontrolling the phase.

[0040] On the other hand, when the dehydration speed selected by theuser is 1000 rpm, the number of the poles of the motor is changed into4, and the input voltage V₃ is applied to the motor, and when thedehydration speed selected by the user is 1200 rpm, the number of thepoles of the motor changed into 4, and the input voltage V₂ is appliedto the motor. In addition, when the dehydration speed selected by theuser is 1400 rpm, the number of the poles of the motor is changed into4, and the input voltage V₁ is applied to the induction motor. That is,the dehydration speed 1400 rpm approximately obtained in the 4 poles ofthe motor can be varied in multiple steps by controlling the inputvoltage applied to the induction motor by controlling the phase.

[0041] Referring to FIG. 2, the steps for calculating the properties ofthe motor (S15 and S19) calculate the dehydration speed sensed by themotor sensor adhered to the motor, and the torque and efficiency of themotor, and the steps for evaluating performance satisfaction (S20 andS16) evaluate performance satisfaction on the basis of the valuescalculated in the steps for calculating the properties of the motor.Here, the routine goes to the final steps or the steps for decidingphase control patterns according to the performance satisfactionresults.

[0042] As discussed earlier, in accordance with the present invention,the method for controlling the dehydration speed of the washing machineconverts the dehydration speed into two-step speed (800 rpm and 1400rpm) by changing the number of the poles of the motor, and controllingthe input voltage applied to the motor by controlling the phase, therebyconverting the dehydration speed in multiple steps.

[0043] Moreover, the method for controlling the dehydration speed of thewashing machine remarkably reduces noises and vibrations of the washingmachine.

[0044] As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

What is claimed is:
 1. A method for controlling a dehydration speed of awashing machine, comprising the steps of: setting the dehydration speedon the basis of an amount of laundry put into the washing machine; andcontrolling a rotation speed of a motor of the washing machine on thebasis of the set dehydration speed.
 2. The method of claim 1, whereinthe step for controlling the rotation speed of the motor comprises thesteps of: changing a number of poles of the motor of the washingmachine; and controlling a voltage applied to the motor when the numberof the poles is changed.
 3. The method of claim 1, wherein the motor isan induction motor.
 4. The method of claim 1, wherein the washingmachine is a drum washing machine.
 5. The method of claim 1, wherein thestep for changing the number of the poles of the motor changes thenumber of the poles into 4 or
 8. 6. The method of claim 1, wherein thestep for changing the number of the poles of the motor comprises thesteps of: sensing a dehydration speed selected by the user; and changingthe number of the poles of the motor on the basis of the senseddehydration speed.
 7. The method of claim 1, wherein the step forcontrolling the voltage applied to the motor comprises a step forcontrolling the dehydration speed of the washing machine, by controllingthe voltage applied to the motor by changing a phase of the voltage whenthe number of the poles of the motor is changed.
 8. The method of claim1, wherein the step for setting the dehydration speed on the basis ofthe sensed amount of the laundry converts the dehydration speed on thebasis of the sensed amount of the laundry.
 9. The method of claim 1,wherein the step for controlling the rotation speed of the motor of thewashing machine on the basis of the set dehydration speed controls thedehydration speed by changing the number of the poles of the motor andcontrolling the phase of the voltage inputted to the motor.
 10. Themethod of claim 2, wherein the step for controlling the voltage appliedto the motor when the number of the poles is changed controls the phaseof the voltage applied to the motor.
 11. A method for controlling adehydration speed of a drum washing machine comprising the steps of:sensing a dehydration speed desired by a user; changing the number ofpoles of an induction motor by the sensed dehydration speed; andchanging a dehydration speed through a phase control of an inductionmotor according to the changed number of poles.
 12. The method of claim11, wherein the number of poles of the induction motor is changed into 4poles or 8 poles.
 13. The method of claim 11, wherein the step forchanging a dehydration speed through a phase control of the inductionmotor comprises the step for varying a voltage according to a sensedfire angle and supplying the voltage to the induction motor.
 14. Amethod for controlling a dehydration speed of a drum washing machinecomprising the steps of: sensing the amount and the quality of thelaundry; determining a dehydration speed according to the sensed data;changing the number of poles of an induction motor according to thedetermined dehydration speed; and changing the dehydration speed througha phase control of a voltage that is inputted to the induction motoraccording to the changed number of poles.
 15. The method of claim 14,wherein the number of poles of the induction motor is changed into 4poles or 8 poles.
 16. The method of claim 14, wherein the step forvarying a dehydration speed through a phase control of the voltagecomprises the steps of: sensing a fire angle corresponding to thedehydration speed; and varying a voltage that is inputted to theinduction motor according to the sensed fire angle.